The Greater New York Autism Research Center of Excellence, a collaborative effort of the Mount Sinai School of Medicine, New York State Psychiatric Institute/Research Foundation for Mental Hygiene, University of Toronto, State University of New York at Stony Brook, and North Shore-Long-Island Jewish Health System, will aim to better understand the functions of the serotonin system in autism, specifically in its relation to repetitive behaviors, by combining methodologies from genetics, functional imaging and neuropsychopharmacology. By investigating core symptom domains of autism and linking this information to etiological factors, the multidisciplinary center's basic science and clinical research will facilitate development of novel or improved strategies for diagnosis, early detection and treatment of autism spectrum disorders. In achieving these goals, the center will be comprised of four integrated cores that will facilitate three interrelated research projects as well as multi-center collaborative endeavors. Project I: Identification of Autism Susceptibility Genes; Project II: Imaging Serotonin Function in Asperger's Disorder; Project Ill: Fluoxetine versus Placebo in Child/Adolescent Autistic Disorder. Core B: Clinical Core; Core C: Data Management and Statistics Core; Core D: Information Transfer Core.